Types of PAP Therapy Devices: CPAP, BiPAP, APAP & More Explained

If your sleep study came back showing obstructive sleep apnea (OSA) or another sleep-related breathing disorder, your doctor has likely recommended Positive Airway Pressure (PAP) therapy. But "PAP" isn't a single device — it's an entire category of treatment technology, and choosing the right type makes a significant difference in how comfortable, effective, and sustainable your therapy will be.

As a licensed Registered Respiratory Therapist (RRT), I've set up thousands of patients on PAP devices. Here's a clear, clinical breakdown of every major PAP device type — what it does, who it's best for, and what to consider before choosing.

CPAP: Continuous Positive Airway Pressure

How It Works

CPAP is the most common PAP device prescribed for obstructive sleep apnea. It delivers a single, fixed pressure throughout the entire night, measured in centimeters of water pressure (cmH₂O). Think of it as a gentle, constant flow of pressurized air that acts like a pneumatic splint, keeping your upper airway open so it can't collapse during sleep.

Prescribed Pressure Range

Most patients are prescribed somewhere between 4–20 cmH₂O. Your specific setting is determined by your sleep study results — either from a titration night in a lab or, increasingly, from an at-home titration using an APAP device (more on that below).

Who It's Best For

• Patients with moderate to severe OSA who have been lab-titrated to a known optimal pressure
• Patients who tolerate a fixed pressure well during their adjustment period
• Those seeking the most widely covered and simplest device option

Key Consideration

CPAP's limitation is its rigidity. If your pressure needs change throughout the night — due to sleep position, REM cycles, or body weight fluctuations — a fixed CPAP can either feel insufficient at times or uncomfortably forceful at others. This is exactly why APAP was developed.

APAP: Auto-Adjusting Positive Airway Pressure

How It Works

APAP (sometimes called Auto-CPAP or AutoPAP) uses onboard algorithms to continuously monitor your breathing and adjust pressure in real time within a prescribed range. If you're sleeping on your back in REM and your airway needs more support, the machine increases pressure. When you're sleeping well and your airway is stable, it backs off. This dynamic adjustment delivers the minimum effective pressure at any given moment.

Who It's Best For

• Patients who haven't had a formal lab titration but have a known OSA diagnosis
• People whose pressure needs vary due to sleep position, alcohol use, or seasonal allergies
• Patients seeking maximum comfort across different sleep stages
• New CPAP users who want a machine that can "find" their pressure during the adjustment period

Key Consideration

APAP is the most versatile entry point for most new PAP users. Many clinicians now skip the lab titration entirely for uncomplicated OSA and start patients directly on APAP, then analyze the data to confirm appropriate settings.

BiPAP: Bilevel Positive Airway Pressure

How It Works

BiPAP delivers two distinct pressure levels: a higher pressure during inhalation (IPAP — Inspiratory Positive Airway Pressure) and a lower pressure during exhalation (EPAP — Expiratory Positive Airway Pressure). This bilevel design makes it significantly easier to breathe against, particularly during exhalation, which some patients find very difficult at higher CPAP pressures.

Who It's Best For

• Patients who require high CPAP pressures (typically above 15 cmH₂O) and struggle to exhale comfortably
• Patients with central sleep apnea, where the brain fails to send proper breathing signals
• Patients with COPD, hypoventilation syndromes, or neuromuscular diseases that affect breathing
• Patients who have tried CPAP and failed due to exhalation discomfort

Key Consideration

BiPAP is considerably more expensive than CPAP or APAP. Insurance coverage typically requires documented CPAP failure or a specific clinical indication. The cost difference between a standard CPAP and a BiPAP can range from $400 to $2,500 or more, depending on the model.

ASV: Adaptive Servo-Ventilation

How It Works

ASV is a highly sophisticated device designed specifically for complex or treatment-emergent central sleep apnea. It continuously analyzes your breathing pattern and delivers targeted pressure support to stabilize your ventilation, preventing both apneas and hypopneas. It essentially "learns" your normal breathing rhythm and compensates for deviations from it.

Who It's Best For

• Patients with Cheyne-Stokes respiration
• Patients who develop central apneas after starting CPAP therapy (treatment-emergent central sleep apnea)
• Complex sleep-disordered breathing cases that don't respond to standard PAP therapy

Important Warning

ASV is contraindicated in patients with symptomatic heart failure with reduced ejection fraction (HFrEF). This is not a device to choose casually — it requires explicit prescription and close clinical monitoring.

AVAPS: Average Volume-Assured Pressure Support

How It Works

AVAPS (also marketed as iVAPS or VAPS-TE depending on manufacturer) targets a specific tidal volume — the amount of air moved with each breath. It adjusts pressure support automatically to ensure your lungs receive an adequate volume of air per breath, even if your breathing effort changes.

Who It's Best For

• Patients with obesity hypoventilation syndrome (OHS)
• Patients with neuromuscular disease (ALS, muscular dystrophy)
• Patients with COPD with hypercapnia (elevated CO₂)

This is a highly specialized device typically managed in close coordination with a pulmonologist or sleep medicine physician.

Key Features to Evaluate Across All PAP Devices

Integrated Humidification

Nearly all modern PAP devices include a heated humidifier. This is not optional — dry pressurized air causes nasal and throat irritation, which is one of the top reasons patients abandon therapy. If you live in a particularly dry climate, look for machines with heated tubing (like ResMed's ClimateLineAir) for superior moisture control.

Data Connectivity

The best CPAP machines now transmit nightly therapy data via cellular or Wi-Fi to cloud platforms. This allows your respiratory therapist or physician to remotely monitor your AHI (Apnea-Hypopnea Index), leak rates, and usage hours without requiring in-office visits. For compliance purposes, this data is often required by insurers.

Noise Level

Modern PAP devices are remarkably quiet, typically operating at 25–30 decibels. But if you or your bed partner are sensitive to sound, compare the decibel ratings across models before purchasing.

Which PAP Device Is Right for You?

If you have straightforward OSA and are just starting therapy, an APAP device is the most flexible and forgiving option. If you're upgrading from an older CPAP and know your pressure needs, a modern fixed CPAP may serve you well. If you've struggled with exhalation or have been told you need bilevel support, a BiPAP is worth the investment.

The best decision is always made with clinical guidance. Our $49.99 Respiratory Therapist Consultation is designed exactly for this — a licensed RRT will review your sleep study data, discuss your history, and give you a clear recommendation based on clinical evidence, not commission.

Browse our full selection of CPAP, APAP, and BiPAP machines — we carry devices across all major categories with transparent pricing and full manufacturer warranties.

Want to understand more about the condition driving your treatment? Read our comprehensive guide on sleep apnea: symptoms, causes, and treatment options. And if you're comparing cash pay versus insurance for your new device, see our breakdown in CPAP cash pay vs insurance.